1. Field of the Invention
This invention relates generally to monitored servo systems and particularly to dynamically controlled monitors for servo systems. More particularly, this invention relates to apparatus for maintaining a close static monitor tolerance under dynamic conditions.
2. Description of the Prior Art
In servo systems incorporating monitoring apparatus, the tolerance of the monitoring apparatus is equal to the static offset error plus the velocity lag error of the system. Prior to the present invention the tolerance of the monitoring apparatus, i.e., the failure detection sensitivity of the apparatus, was set wide enough to accommodate the velocity lag error component in order to forestall nuisance failure alarms under dynamic conditions. However, this desensitizes the monitoring apparatus under static conditions, and in many applications such desensitization cannot be tolerated. The present invention overcomes this disadvantage by using rate feedback to compensate for the velocity lag error component, whereby the tolerance of the monitoring apparatus can be held closer than has heretofore been possible in order to achieve the required static sensitivity.